Transcript Eighth lecture

Eighth lecture
Radiation syndromes and stages
in human
• A syndrome is a combination of symptoms
resulting from a single cause and
occurring together so as to constitute a
single clinical picture.
• Large acute whole-body exposures in man
may result in one of the three radiation
syndromes:
i-Hematopoietic syndrome.
ii-Gastrointestinal tract syndrome.
iii-Central nervous system syndrome.
Hematopoietic system syndrome.
Progress of the hematopoietic system syndrome:
i-Prodromal stage:
following dose of 2-10 Gy.
NVD will occur within 1-5 days.
ii-Latent phase: will last 1-3 weeks.
iii-Illness: NVD, fatigue, anemia, fever, epilation,
anorexia & petechial hemorrhaging on skin.
iv-Death:
occurs within 2-6 weeks.
the most probable causes of death will be :
hemorrhage and infection.
Gastrointestinal tract syndrome
Progress of the GIT syndrome:
i-Prodromal stage: following dose of 10-50 Gy.
It lasts 1-3 days, within 2 hrs loss of appetite,
upset stomach & apathy. Several hrs later, NVD
will occur.
ii-Latent phase:
will last 1-7 days after prodromal St.
iii-Illness:
NVD, fever, apathy, anorexia & loss of wt.
iv-Death:
occurs within 3-12 days.
the causes of death include fluid and electrolyte
losses (circulatory collapse)
Central nervous system syndrome
• Is produced by acute whole-body exposures above
50 Gy
• Survival is impossible.
• Death results from respiratory failure and/or brain
edema caused from direct damage to brain or
indirect damage mediated by effects on the blood
vessels of the brain.
• Within hrs, symptoms become very severe; they
include V&D, apathy, disorientation & tremors.
• The victim is likely to fall into a coma.
The effects of radiation on biological
systems: Tissues
Hematopoietic System
• Are the cells of the hematopoietic system
and related lymphoid system.
• Are highly sensitive to radiation killing.
• Most sensitive cells are:
i-The stem cells of the bone marrow.
ii-The lymphoid tissues found in the spleen,
liver, lymph nodes and thymus.
Hematopoietic system
• Circulating lymphocytes are quite sensitive to
radiation.
• 10 cGy can show a measurable drop in the
circulating small lymphocyte population.
• Of particular resistance are the mature
circulating red blood cells and platelets.
• The effect is pan-cytopenia (depression of all
cell types), resulting in hemorrhage (platelet
reduction), infection (white-cell depression), and
the effect of anemia from plummeting red cells.
Gastrointestinal system
• The GIT is highly sensitive to
radiation.
• The first changes seen occur in the
epithelium lining of the villi.
• Radiation causes mitotic arrest of the
crypt cells followed by eventual
denudation of the villi, ulceration of
the wall, and septic infiltration.
Gastrointestinal system
• Effects on the large intestine cause
functional impairment resulting in fluid
and electrolyte loss, and diarrhea.
• Effects on the upper GI tract include
vomiting, depression of acid, and pepsin
secretion. Destruction of the epithelium
lining of the pharynx and esophagus
results in dryness, soreness, and
petechia (capillary rupture).
Central nervous system
• CNS & PNS are resistant to radiation effects.
• Very high doses are required to cause
substantial effects on the brain and nervous
system.
• Effects on the vessels cause breakdown of
the blood capillaries, interstitial edema, and
the breakdown of the blood-brain barrier.
• The spinal cord exhibits radiation effects
including thickening of the vessels,
dissolution of white matter
•